1. Field of the Invention
The present invention relates to a reconfigurable logical device, and in particular it relates to a technique of inspecting configuration data of the reconfigurable logical device.
2. Description of the Related Art
In a device (reconfigurable logical device), such as an FPGA (Field Programmable Gate Array) of which a circuit logic can be changed based on configuration data (circuit information data), the configuration data, if not correct, will be a cause that damages the device. For example, when both pads (pins), which are input-output parts of an FPGA chip, and a peripheral circuit, which is connected thereto, are in output states, there will be a high probability that the device will be damaged.
An FPGA can be used for the purpose of changing and/or updating the function of a product by causing its configuration data to be downloaded after the shipment thereof. For example, with an in-vehicle device using an FPGA, the function thereof can be changed by downloading its configuration data via a wireless network or a recorded storage medium from the outside of a vehicle. At the time when such configuration data is downloaded, an alteration or falsification by a third party will pose a problem. It is considered that with an intention to destroy the device, a third party may alter or falsify the configuration data so as to place both the pads of the FPGA and its peripheral circuit into their output states, as mentioned above.
In order to verify the alteration of the configuration data by such a third party, there have been proposed methods that make use of encryption technology (Japanese patent application laid open No. 2003-122442, and Japanese patent application laid-open No. 2003-304235). In these methods, the detection of an alteration of configuration data is made possible by applying an electronic signature to the configuration data by the use of encryption technology.
However, the methods of verifying configuration data using an electronic signature are carried out on a large scale, and will cause an increase in cost, etc.
An object of the present invention is to provide a technique that is capable of inspecting the configuration data of a reconfigurable logical device by the use of a simple method.